Effect of stem length _ help choose a Genesis io id

I'm considering a Genesis io id as a do it al bike to replace my 29er Kona Unit. Beimg 5'10/5", I can ride either a 17.5" or a 19" with suitable stem adjustment. My stock Kona was a the 18" frame with a 100mm (I think) stem and a 59.7cm effective top tube.

The Genesis has ETT of 58.5 or 600, meaning stems of 110 or 90 mm respectively. What would be the effect of either choice? In general is it better to go for a shorter stem and longer ETT? Will the smaller wheels and shorter stem make handling much more lively? The Kona was my introduction to MTB's, and the current one has a lot lower spec than my old one. I'm wheel size agnostic (26er curious if you like), and fancy suspension for a change, and the possibility of conversion to a 69er if needed.

I looked at the archives and in previous sizing threads, both frames were recommended in separate threads

Where are you based? I have a 17" io in brighton. It came with a long 90ish mm stem and flat bars and 100 mm forks which felt like it would just eat up miles. I now have higher rise bars, short 50mm stem and forks at 120mm forks for riding around in the woods. I am 5'10" ish if that helps at all?

To put a 110mm stem on one will slow the handling down somewhat from its original design

I've got a 17.5" Genesis Altitude with an 80mm stem and it handles superbly, but if anything, they are a few mm shorter than many of their competitors in the TT length. I'd go for the 19" in your case and run it with an 80mm stem.

Tired, you're three inches taller than me - but getting a far bigger frame than I rode. I'd strongly suggest at least test riding a 17.5" - I rode a 16" for a very long time and loved it. As said above, stem length is affected by a bunch of things, so I'm not saying 17.5 is *definitely* for you, or that you must chops stems around. But 100m is a long stem on a modern mountain bike design.